The Epidemiology Branch (EBRP) is designing a case control study to examine the effect of vitamin-folate supplements in the periconceptional period and neural tube defect risk. Drs. Mills and Rhoads are planning a telephone interview study in which mothers who have delivered a child with a neural tube defect (defined as cases), mothers who have delivered a child with another malformation (defined as controls), and mothers who have delivered a normal child (defined as controls) will be compared on the use of vitamins in the period around conception. Prospective study centers and data centers have been selected by reviewers. Negotiations are in progress. Depending on the availability of funds, the study will begin in the fall of 1984 or winter of 1984-85.